Protective Shield for Thermal and Acoustic Shielding of Components of an Internal Combustion Engine

ABSTRACT

The invention relates to a protective shield for the thermal and acoustic shielding of a components of an internal combustion engine, comprising a metal net with a multiplicity of through apertures; at least on absorber layer of a sound-absorbing material; and a carrier plate; wherein the metal net is arranged on the side of the protective shield facing the component; the at least one absorber layer is arranged between the metal net and the carrier plate; and the carrier plate in its edge region is folded over about the edge of the metal net.

The present invention relates to a multi-layer protective shield which serves for the thermal and acoustic shielding of components of an internal combustion engine and of turbochargers, catalytic converters, exhaust manifolds and the like.

Shields of this type are used on motor vehicles but also comparable machines for heat and sound shielding of components. Such components are mainly constituent parts of the exhaust system, i.e. catalytic converters, exhaust manifolds, turbochargers and the like. The shields are to shield the interior space of the vehicle against the high temperatures and the sound that develops through vibrations that occur. In order to meet the ever more stringent regulations in terms of the external sound level of vehicles the shields are to preferably absorb, i.e. not simply reflect noises.

Since the mentioned components can get very hot in operation, thermal shielding is indispensable in order to prevent that other vehicle components are detrimentally affected by the high temperatures. However, an application can also consist in conversely thermally shielding the section of the exhaust system from the engine as far as to the catalytic converter. Since such exhaust catalytic converters require a certain minimum temperature for their correct and best possible functioning, faster reaching of the operating temperature can be achieved through such “converse” shielding. As a result, the exhaust values of the respective vehicle can be improved.

Corresponding shields can also be used in the engine compartment in order to protect components such as for example plastic hoses, electrical wiring, engine electronics etc. against excessive temperatures. There is a plurality of possibilities for achieving thermal shielding. One of these consists in the use of heat-insulating materials in the shield, for example foam-like materials or fibre materials which, because of their comparatively large content of air, are poor heat conductors.

Another or additional possibility is to reflect the heat radiation from hot components on the shield, which for instance can be achieved through metal coatings. Such reflection is most easily achieved through a solid plate. Such air and thus sound-impermeable plates however are disadvantageous with regard to sound insulation, since the sound is substantially reflected completely. In unfavourable cases even resonance can be caused which brings about droning and similar undesirable acoustic effects.

Acoustic shielding can be obtained through special sound-absorbing surface structures, but this is generally difficult to establish and/or requires certain minimum thicknesses of the corresponding layers, which is a disadvantage in the partly confined conditions in modern vehicles.

Another possibility therefore consists in using a material with permeable pores. Within such pores the mechanical energy of sound waves can be converted into heat through friction, so that acoustic shielding is obtained. Through the air content in the pores, thermal insulation is additionally achieved.

A shield, which is to comprise both good acoustic as well as thermal shielding characteristics, is therefore generally composed of various materials in accordance with the problems discussed above. In addition, such a shield must still have additional mechanical characteristics.

These include stability with regard to the mechanical loads that occur when operating a vehicle, i.e. the fatigue strength of the fastening points. In addition, installing such a shield should be preferably simple and safe, i.e. it is preferred that no sharp edges are present whatsoever which can cause injuries to persons or damage to other vehicle components.

A multi-layer shield, having layers of various materials, should additionally be producible in the simplest manner possible and with few steps.

It is therefore an object of the present invention to provide a heat and sound protective shield which has both good thermal as well as acoustic shielding characteristics and good mechanical stability, which is easy to manufacture and handle.

According to an aspect of the present invention a protective shield is provided for the thermal and acoustic shielding of a component of an internal combustion engine. The protective shield comprises a metal net with a multiplicity of through apertures; at least one absorber layer of a sound-absorbing material; and a carrier plate. Here, the metal net is arranged on the side of the protective shield facing the component, the at least one absorber layer is arranged between the metal net and the carrier plate and the carrier plate in its edge region is folded over the edge of the metal net.

Through this arrangement an effective acoustic/thermal shield is provided, which is easy to manufacture, has good mechanical stability and can be handled without the risk of injuries to persons or damage to other vehicle parts.

In a preferred embodiment the metal net has a depression wherein the at least one absorber layer is arranged within said depression. As is shown in more detail in the following description of preferred embodiments, this embodiment provides advantages in both the manufacture as well as the operating characteristics of the shield according to the invention.

In a preferred embodiment the distance between the metal net and the carrier plate within the depression amounts to at least approximately 5 mm.

In a preferred embodiment the overall area of the through apertures in the metal net amount to between 20 to approximately 30% of the total area of the metal net.

In a preferred embodiment the carrier plate is an aluminized steel plate with a thickness of approximately 0.4 mm. The coating can be provided as corrosion protection but also improve the heat reflection of the shield.

In a preferred embodiment the metal net comprises a wire mesh of aluminized metal wire. A wire mesh can be produced easily and cost-effectively and can be protected against corrosion through the aluminising, while the coating can also be advantageous for increasing the heat reflection. In another preferred embodiment the metal net comprises a wire mesh of galvanized metal wire. In a further preferred embodiment the metal net comprises a wire mesh of stainless steel wire, wherein in this case no corrosion protection whatsoever is necessary.

In a preferred embodiment the sound-absorbing material comprises a fibre material, which can be basalt wool with a specific weight of approximately 950 g/m³. In another preferred embodiment the sound-absorbing material comprises a foam rubber material which can be melamine foam.

In a preferred embodiment the at least one absorber layer is a multi-layer composite layer.

In a preferred embodiment the carrier plate on the side facing the at least one absorber layer comprises a sound-absorbing surface structure. As a result, sound absorption can be improved.

In a preferred embodiment fastening means are provided in the edge region in order to attach the protective shield. The edge region is particularly suited to provide such fastening means therein, because of the good stability and durability in the folded-over region.

The present invention is explained in more detail in the following making reference to the enclosed drawings, wherein

FIG. 1 shows an embodiment of the present invention in cross section; and

FIG. 2 shows an alternative embodiment of the present invention in cross section.

FIG. 1 shows an embodiment of the protective shield according to an invention in a cross-sectional view which is arranged as shield of a component 8 of an internal combustion engine. The component 8 can for example be a turbocharger, a catalytic converter or another component which gets hot in operation, i.e. constitutes a source of heat. The heat output is frequently also connected with sound radiation such as is the case for example with silencers or turbochargers.

The term “porosity” is used in the following in connection with the present invention. Porosity according to the invention means the part of the metal net or mesh which is permeable, i.e. the component of the area of such a layer that is assumed by through apertures based on the total area of the respective layer.

Facing the heat source 8 is located a permeable metal net 2 such as wire mesh or netting. The metal net 2 thus has through apertures which are thus “porous” or air-permeable. On the side of the metal net 2 facing away from the component 8 is located at least one absorber layer 4 which has a sound-absorbing function. This layer 4 can be a composite layer. The shielding element according to the invention is enclosed by a carrier plate 6.

The carrier plate 6 is folded over about the layer 2 in its edge region 10 (indicated by the dashed circle). In the embodiment shown here the edge region 10 is only folded over about the metal net layer 2. The metal net 2 forms a depression or pocket in which the absorber layer 4 is located. Forming such a pocket facilitates the manufacturing process of the shielding element according to the invention, since the absorber layer in this case can be inserted easily and thus is already fixed in a preliminary manner. In other words it is easier to arrange the layers on top of one another as an accurate fit when producing the shield than without such a pocket.

However, the invention is not restricted to this embodiment; in other embodiments (not shown) no such pocket is present, in this case the absorber layer 4 and the metal net layer 2 lie on top of each other over their entire area. In this case the carrier plate 6 is then folded over also about the edges of both layers 2,4. Since in this case the absorber layer at its edges is additionally clamped in between carrier plate 6 and metal net layer 4, slipping of the absorber layer 4 can be effectively prevented with such an embodiment.

The protective shield according to the invention possesses a double shielding effect against heat and sound radiation. Here it must be noted that for heat radiation a type of shielding other than for sound is desired. While with heat radiation it is desirable to reflect such heat radiation to the greatest possible extent, i.e. to discharge it to the environment, exactly the opposite effect is desirable in the case of sound. Sound waves are not to be reflected, which increases the external noises of the vehicle and in unfavourable cases can also result in resonances (“droning”), but instead are to be completely absorbed if possible.

On the one hand (mechanical) sound waves are converted in the metal net 2 into heat through friction, while on the other hand (electromagnetic) heat radiation is reflected to a certain degree through the non-permeable component of the area of the metal net 2. This effect can be further increased through suitable coating. The absorber layer 4 is provided in order to absorb remaining sound and residual heat (which is also transmitted through convection). The carrier plate 6 then forms the enclosing barrier for sound and heat.

Through the distance between carrier plate 6 and metal net 2 (depending on embodiment within the pocket formed or in other embodiments over the entire area) the effectiveness of the shield can be adapted to certain frequency ranges. Greater distances shift the frequency absorption curve towards lower frequencies and vice versa. This is advantageous since depending on the component to be shielded a specific frequency range can be covered. For example in the case of turbochargers rather high frequencies (“whistling”) occur because of their high speed while other sections of the exhaust system generate comparatively lower frequencies.

In the embodiment shown in FIG. 1 this distance can be advantageously determined through the depth of the pocket. Since metal net and carrier plate as a rule will be clearly more compression-resistant than for example the absorber layer consisting of foams, a defined distance for the intended frequency range can be easily maintained in this way whereas without such a pocket the absorber layer would be deformable to a greater extent. Through the deformation, i.e. flattening of the absorber layer the defined distance would be changed or reduced so that frequencies other than the desired ones would be absorbed, while the frequencies actually to be shielded would then be allowed to pass through to an undesirably greater degree.

Thus, through the embodiment shown in FIG. 1 a shape-retaining protective shield is obtained that will not substantially change the distance between carrier plate and metal net even in operation. The folding over or flanging over of the carrier plate makes possible simple and cost-effective manufacture of the multi-layer protective shield. In addition, the handling especially during assembly is facilitated since the folded-over region encloses sharp edges of the metal net. In the edge region fastening means can also be provided in a simple manner (not shown), which make possible secure fastening of the protective shield and which show no tendency to tear out during continuous operation. Such fastening means can for example be bores for screws, rivets or the like which are provided in the edge region.

FIG. 2 shows an alternative embodiment of the protective shield of FIG. 1. Here, a sound-absorbing surface configuration or structure 12 is additionally present on the inner side of the carrier plate 6. This structure 12 for example can be provided through punching-in or the like in the carrier plate 6. As a result, the sound absorption of the shield according to the invention is further improved. An additional advantage with a structure as shown here consists in that slipping of the absorber layer 4 is additionally reduced. By providing a surface structure the adaptation of the absorption curve can also be improved.

In all embodiments of the invention adaptation of the sound absorption can also be easily obtained in that the metal net is rolled to a desired porosity, i.e. the pore sizes are brought to desired values through rolling or the like.

A multi-layer heat protection shield for use in the vehicle engine region is described in the present invention, for the thermal and acoustic shielding of hot components such as turbocharger, exhaust manifold etc. The sound-absorbing effective heat shield comprises at least 3 layers.

Here, the layer facing the sound/heat source is a metal net, e.g. a metal wire mesh or netting. This is followed by one or a plurality of layers of an absorber material for sound absorption. Finally, the absorber layer(s) is followed by a metal plate (for example an aluminized steel plate of 0.4 mm thickness), which holds together the layer composition through folding over of the edge region at least about the metal net.

As a result it is prevented that an exposed edge of the netting results in sharp edges and thus constitutes potential risk of injury or the risk of damaging other vehicle parts. The folded-over edge region ensures easier and more secure handling during the assembly of the shield according to the invention. The folding-over also gives the shield greater stiffness and increased durability during continuous engine operation.

The metal wire mesh layer can be embodied as regular or irregular netting, i.e. the size and arrangement of the through apertures or “pores” is either regular or irregular. “Porosity” in terms of the present invention must be understood as the total area of the through apertures based on the total area of the mesh layer. Through its porosity (20 to 30%) the netting is able to convert impinging sound waves into heat through friction, thus damping said sound waves.

Here, the regular or irregular distances or the size of the pores of the netting can be configured depending on the frequency range of the sound waves to be shielded. An additional possibility of influencing the porosity (adaptation to different frequencies) of the netting can be effected through flat-rolling or compressing to various thicknesses of the netting, as a result of which the porosity can be changed. As a result of this, additional stiffness of the netting can be achieved in addition.

In order to guarantee the corrosion resistance of the netting it is advantageous to additionally coat the netting with zinc or aluminium. Nettings of stainless steel require no such coating. In addition to the above-mentioned tasks the netting layer should additionally ensure the accommodation of the absorber material during the manufacturing process of the shield.

To this end, a type of depression or pocket for example in the depth of the thickness of the absorber material, is pressed into the netting into which the absorber material can be placed. The depth of the pocket produces a defined distance of the mesh layer to the terminal or carrier plate, which in a preferred embodiment should at least amount to 5 mm. The greater the distance between the netting and the terminal plate is selected, the more the frequency absorption curve is displaced to lower frequency ranges. Thus the absorption can be suitably adapted to the requirements through suitable selection of this distance.

The absorber material in the multi-layer construction of the shield assumes the task of the residual absorption of the sound waves that pass through the netting. To this end, fibre materials (for instance basalt wool 960 g/m³) or foams (for example melamine foam) can be used. In order to be able to shift the degree of absorption into desired frequency ranges, the absorber material can be single or multi-layered. It can also have different densities in the layer composition in order to be able to cover as wide as possible a frequency range.

Through additional coating of the netting the reflection of the heat can be additionally increased and the thermal shielding effect improved as a result.

By using temperature-resistant materials for the outer layers in conjunction with basalt or silica fibres for the absorber layers of the shield according to the invention, direct screwing to hot engine components such as turbochargers, manifolds, catalytic converters, silencers etc. is possible. In contrast, shields acting acoustically and thermally in a conventional manner can only be installed on cold vehicle components such as body, hoods, plastic parts etc. 

1. Protective shield for the thermal and acoustic shielding of a component of an internal combustion engine, comprising: a metal net having a multiplicity of through apertures and an edge; at least one absorber layer of a sound-absorbing material; and a carrier plate; wherein the metal net is arranged on the side of the protective shield facing the component; the at least one absorber layer is arranged between the metal net and the carrier plate; and an edge region of the carrier plate is folded over about the edge of the metal net.
 2. The protective shield according to claim 1, wherein the metal net includes a depression, and the at least one absorber layer is arranged within this depression.
 3. The protective shield according to claim 2, wherein the metal net is spaced from the carrier plate within the depression by at least about 5 mm.
 4. The protective shield according to claim 1, wherein the total area of the through apertures in the metal net equals about 20 to 30% of the total area of the metal net.
 5. The protective shield according to claim 1, wherein the carrier plate comprises an aluminized steel plate with a thickness of about approximately 0.4 mm.
 6. The protective shield according to claim 1, wherein the metal net comprises a wire mesh of aluminized metal wire.
 7. The protective shield according to claim 1, wherein the metal net comprises a wire mesh of galvanized metal wire.
 8. The protective shield according to claim 1, wherein the metal net comprises a wire mesh of stainless steel wire.
 9. The protective shield according to claim 1, wherein the sound-absorbing material comprises a fiber material.
 10. The protective shield according to claim 9, wherein the fiber material is basalt wool having, a specific weight of about 960 g/m³.
 11. The protective shield according to claim 1, wherein the sound-absorbing material comprises a foam rubber material.
 12. The protective shield according to claim 11, wherein the foam rubber material is melamine foam.
 13. The protective shield according to claim 1, wherein the at least one absorber layer is a multi-layer composite layer.
 14. The protective shield according to claim 1, wherein the carrier plate on the side facing the at least one absorber layer comprises a sound-absorbing surface structure.
 15. The protective shield according to claim 1 including fastening means. 